ChandraObservations of the Gravitational Lenses B1600+434 and B1608+656

We observed B1600+434 and B1608+656 with CXO/ACIS, detecting both quasarimages in B1600+434 and three of four images in B1608+656. We did not detectsignificant X-ray emission from nearby galaxy groups or clusters associatedwith each lens galaxy. The upper limits on the X-ray luminosity of any clusterwithin 4 arcmin of each lens and at each lens redshift are of ~2\times10^{42}and ~6\times10^{42} erg/s for B1600+434 and B1608+656, respectively. Theradio-loud source quasars have power-law photon indices of \Gamma=1.9\pm0.2 and\Gamma=1.4\pm0.3 and X-ray luminosities of 1.4^{+0.2}_{-0.1}\times10^{45} and2.9^{+0.7}_{-0.4}\times10^{44} erg/s for B1600+434 and B1608+656, respectivelybefore correcting for the magnification. We detected a differential absorptioncolumn density of \Delta N_H ~ 3\times10^{21} cm^{-2} between the two images ofB1600+434, roughly consistent with expectations from differential extinctionestimates of \Delta E(B-V)=0.1 mag and a standard dust-to-gas ratio. Thedifferential absorption observed in gravitational lenses may serve as animportant probe to study the gas content in high redshift galaxies since it canseparate the absorbing column originating from the lens galaxy and thoseintrinsic to quasars. We also detected 157 serendipitous X-ray sources in thetwo Chandra fields and identified the brighter optical counterparts using theSDSS and DPOSS surveys.Comment: 24 pages, including 3 figures and 5 tables, accepted by Ap